This invention relates to an apparatus for taking out and conveying, in a dust-proof state, an original such as a photomask or a reticle (which will be referred to simply as "mask") used in a semiconductor printing apparatus, and to a cassette for containing therein an original in a dust-proof state.
Manufacture of semiconductor elements such as integrated circuits (IC), large scaled integrated circuits (LSI), super large scaled integrated circuits (SLSI) and the like involves various problems to be solved. One of them is deposition of dust or foreign materials on the mask.
When a very fine pattern of such semiconductor integrated circuit is to be printed on the wafer and where any foreign material is deposited on the mask, the transferred semiconductor circuit pattern will be damaged. This leads not only to deterioration of the semiconductor, but also, in the worst case, to uselessness of the semiconductor.
The above problem is quite serious particularly in a projection exposure apparatus of step-and-repeat type (repeated exposure type), since in such exposure apparatus the semiconductor integrated circuit pattern of one mask is repeatedly printed on one wafer so that any foreign material deposited on the mask will damage all the chips of that wafer. Considering such problem of deposition of foreign materials, it is desired that the mask is kept as much as possible away from human beings which are a source of foreign materials.
In conventional exposure apparatuses, however, the mask has to be located at the exposure station by the manual labor of the operator so that it is difficult to prevent deposition, on the mask, of the foreign materials from the body of the operator.
Because of such limitation to the prevention of dust deposition in the conventional mask handling manner, development of a feeding system which ensures automatic mask feeding without relying on the manual labor of the operator is strongly desired, particularly in a projection exposure apparatus of the stop-and-repeat type.